The present invention relates in general to the drilling of core samples, and in particular to the stabilization of the recovered core in a core barrel.
Cores (drilling core samples) acquired in the subsurface of the earth are generally recovered with a core barrel that either has a disposable inner barrel or a disposable inner barrel liner. (For the purposes of the present invention, the distinction is not material, and xe2x80x9cinner barrel,xe2x80x9d will be used to refer to both a disposable inner barrel and a disposable inner barrel liner.) At the surface, the core barrel is separated from the coring assembly and placed on the drilling rig floor or other work area.
If the core material is unconsolidated, the core is xe2x80x9cstabilizedxe2x80x9d to prevent mechanical damage caused by handling and shipment. Core stabilization may either be by freezing with dry ice to artificially consolidate the core, or by filling an annular space of the core barrel with a non-reactive core stabilizing compound, for example, epoxy or gypsum. FIG. 1 illustrates, in transverse cross section, an inner barrel 102, enclosing a core sample 104. Because core sample 104 does not completely fill inner barrel 102, a void space 106 remains in an interior of inner barrel 102, which may be filled to prevent core sample 104 from moving within inner barrel 102, to prevent damage to the core by handling and shipment of the samples. In both the epoxy fill or gypsum fill techniques, the inner barrel, which may be thirty feet or more in length, is first sectioned into approximately one meter segments. Each segment is placed on a rack in a near horizontal position to drain any drilling fluid, or mud, from the inner barrel. The base of the segment is then stabilized. After the base is stabilized, the segment is placed in a near vertical position and the entire segment stabilized. Thus, the present methodologies entail substantial handling of the inner barrel and enclosed core sample, and the sample is thus susceptible to mechanical damage caused by vibration, jarring, or other movement.
Thus, there is a need in the art for apparatus and methods that reduce the risk of core damage and the stabilization of core samples in inner barrels. In particular, there is a need in the art for techniques that reduce the movement and handling of the inner barrel, and the contained core in the stabilization process, and, which advantageously permits stabilization of the full length of the inner barrel without the need for segmenting the inner barrel and contained core sample.
The present invention provides a core stabilization mechanism which stabilizes the core along the entire length of the inner barrel. At each one of a plurality of positions spaced axially along the inner barrel, a set of ports are provided. The ports are displaced circumferentially about the inner barrel at each axial location. One port of the set provides a vent port, and the others provide drainage and injection ports. During the stabilization process, air, or other gas, is injected into the vent port, via a gas manifold attached thereto, thereby effectuating the drainage of the drilling mud from the drainage/injection ports. After the drilling mud has been drained, a core stabilizing compound is simultaneously injected into all of the drainage/injection ports, at each position along the length of the inner barrel. An injection manifold is attached to a drain/inlet coupled to each drainage/injection port. The injection manifold is fed from a stabilizing compound supply. The core stabilizing compound is then allowed to cure. After curing, the inner barrel, with the stabilized core contained therein may be sectioned into segments for ease in handling and transport.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention.